Electric circuit



Aug. 13, 1935. B. M. CAIN 2,011,395

ELECTRIC CIRCUITS Filed Aug. 12, 1933 Inventor Bernard Mcai 5 *1 HisAtborhe y.

Patented Aug. 13, 1935 PATENT OFFICE ELECTRIC CIRCUIT Bernard M. Cain,Ballston Lake, N. Y., asalgnor to General Electric Company, acorporation oi.

New York Application August 12, 1933, Serial No. 884,886

12 Claims.

My invention relates to electric circuits and more particularly toarrangements for improving the operating conditions of circuitcontrollers.

When circuit controllers are used intermittently iiv to control thecurrent flow in a circuit they are often shunted by an energy storagedevice for the purpose of improving the operating condition of thecontroller. Thus it is quite common to connect a capacitor (electriccondenser) across the contacts of a make and break switch in order toreduce the sparking at the contacts. The operation is such that when thecontacts first open the voltage drop across the condenser will be lowand consequently there will be insufl'lcient voltage to produce ormaintain an are or spark. However, when the contacts again close, thecondenser, which has been charged while the contacts are open,discharges through them thereby delivering a high current and causingdamage to the contacts.

In accordance with my invention I provide means for preventing the abovedescribed discharge of the energy storage device through the circuitcontroller. In a preferred form this means comprises an asymmetricalconducting device, preferably a unidirectional conducting device, suchasa half wave rectifier, connected between the energy storage device andthe circuit controller with its direction of lesser or non-conductivitysuch as to block the discharge current from the energy storage device.It is also desirable in most cases to connect an impedance, such as arelatively high resistance, across the energy storage device so that itcan discharge through this impedance at the proper time.

An object of my invention is to provide a new and improved electriccircuit arrangement.

Another object of my invention is to provide means for improving theoperating condition of circuit controllers. Another object of myinvention is to provide means for preventing contact shunting condensersfrom discharging through their associated contacts.

My invention will be better understood from the following description,taken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

In the drawing, in which like reference characters refer tocorresponding parts in the two figures,'Fig. 1 is a diagrammatic showingof an embodiment of my invention, and Fig. 2 is a diagrammatic showingof an application of the arrangement of Fig. 1 to an automatic voltageregulator for a direct current shunt generator.

Referring now to Fig. 1 of the drawing, I have shown therein an electriccircuit I having connected therein a switch, or circuit maker andbreaker, comprising contacts 2 and 3, of which contact 3 is movable intoand out of engagement 5 with contact 2. Connected across the contacts 2and 3 is a condenser l and connected between the contacts and thecondenser is a unidirectional conducting device 5. Connected across thecondenser is a resistor 6.

In order to facilitate a description of the'operation of Fig. 1, it willbe assumed that circuit l is a direct current circuit whose polarity isas indicated, and it will also be assumed that the direction oiconductivity of unidirectional conducting l5 device 5 is in thedirection of the arrow head forming part of the symbol for this device.Under these circumstances and assuming that circuit I is energized by asuitable source of direct current (not shown) so as to have the polarity20 indicated, all of the current will flow through the contacts 2 and 3,as they are shown in engagement in this figure. If now contact 3 ismoved out of engagement with contact 2 the condenser 4 will momentarilyabsorb the current in a well known manner and this current will flowthrough the unidirectional conducting device 5. The initial voltage dropacross the condenser I will be relatively small and consequently therewill be insumcient voltage to produce an injurious are between thecontacts 2 and 3 when they are separated. The condenser 4 will soonbecome charged whereupon the current in circuit i will have to flowthrough the impedance 6 and the current in circuit I may be madesubstantially any value desired by choosing a suitable value for theimpedance 6. If now contact 3 is moved into engagement with contact 2the condenser I would ordinarily tend to discharge through the contacts2 and 3 thereby sending a relatively heavy current through thesecontacts. However, this action is prevented by the unidirectionalconductive device 5, which as shown, is so connected that dischargecurrent from the condenser cannot flow through the contacts 2 and 3.Consequently, the condenser 4 will have to discharge through theimpedance 6.

It should be understood that in its broadest aspects, my invention isnot limited to the use of the'impedance 6 and that without thisimpedance the unidirectional conducting device will still prevent thecondenser 4 from discharging through the contacts 2 and 3 when theyengage each other. V However, for intermittent action of the contacts itis preferable to provide an impedance across the condenser 4 so that thecondenser may discharge through the impedance whenever the contactsengage. Otherwise, the condenser 4 would remain charged so that it couldnot perform its proper function upon a second separation oi thecontacts.

In the application of my invention shown in Fig. 2 the circuit Icomprises the shunt field winding circuit of a direct current generatorI having a shunt field winding 8. In this application the resistance 6becomes the regulating resistance for a vibratory contact voltageregulator whose contacts are 2 and 3 and which contacts are actuated bya voltage responsive magnet I connected to respond to the voltage ofgenerator I. Contact 3 is mounted on a suitable support such as a bladespring III which biases contact 3 into engagement with contact 2.

In the operation of Fig. 2 it will be assumed that generator I is beingdriven by a suitable prime mover (not shown). With the contacts 2 and 3in engagement as shown, the regulating resistance I is short clrcuitedand consequently the maximum current tends to fiow through the shuntfield winding 3 and through the contacts 2 and 3. This increases thevoltage 01' generator 1 until a predetermined, or normal, voltage isreached at which voltage the energization oi magnet 9 becomes strongenough to cause contacts 3 to leave contact 2. When this happens. thecurrent momentarily flows through the condenser thereby permitting thecontacts I and 3 to break without producing a spark and in a short timethe condenser 4 becomes charged and the field current is reduced to arelatively low value because it must flow through the resistor 3.Consequently, the voltage of generator 1 falls and as soon as it fallsbelow the normal value the pull of magnet 9 becomes weakened so that thespring It causes contact 3 to engage contact I. This short circuits theresistor again and allows the field current to increase, thereby toincrease the voltage in generator I. At the same time that the contacts2 and 3 close the condenser 4 tends to discharge through the contacts 2and 3 but is prevented from doing so by means of the unidirectionalconducting device I. The action of the regulator is relatively rapid andthe contact 3 vibrates into and out of engagement with contact 2 therebyto hold an average value 01' current in field winding 3 which issufllcient to maintain a relatively steady normal voltage at theterminals of generator 1.

While I have shown and described particular embodiments of my invention,it will be obvious to those skilled in the art that changes andmodifications-ma'y be made without departing from my invention, and Itherefore aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, an electric circuit, circuit ing and breaking meansand said energy storage means for preventing the energy storage meansfrom discharging through said circuit making and breaking means.

3. In combination, an electric circuit, a pair 01 cooperating contactsconnected therein, a condenser connected across said contacts, and meansincluding a unidirectional conducting device for preventing saidcondenser .irom discharging through said contacts when they engage eachother.

4. In combination, an electric circuit, a pair of make and breakcontacts connected therein, a condenser connected to reduce the voltageacross said contacts when they separate, and means including aunidirectional conducting device and an impedance for preventing saidcondenser i'rom discharging through said contacts when they engage eachother. 7

5. In combination, an electric circuit, an impedance connected therein,energy storage means connected across said impedance, a circuitcontroller connected to be capable of short circuiting said impedance,and means (or preventing said energy storage means from through saidcircuit controller when said controller short circuits said impedance.

6. In combination. an electric circuit, an impedance, and anasymmetrical conducting device connected in series in said circuit, anenergy storage device connected across said impedance, and a circuitmaker and breaker connected across both said impedance and saidasymmetrical conducting device.

"I. In combination, a direct current circuit, a resistor connectedtherein, a condenser connected across said resistor, a set ofcooperating contacts connected to be able to short circuit saidresistor, and means for preventing said condenser from dischargingthrough said contacts when they engage each other.

8. In combination, a direct current inductive circuit, a resistor insaid circuit, a pair of intermittently engaged and separated contactsconnected so as to be able to short circuit said resistor, a condenserconnected across said resistor, and means for preventing the dischargecurrent from said condenser from flowing through said contacts when theyengage each other.

9. In combination, a direct current circuit, an asymmetrical conductingdevice and a resistor connected in series in said circuit, a condenserconnected across said resistor, and a set of contacts connected acrosssaid device and resistor.

10. In combination, a direct current circuit, an inductance and aresistor connected in series in said circuit, a unidirectionalconducting device connected in said circuit electrically adjacent saidresistor with its direction of conductivity the same as the direction 0!normal current flow in said circuit, a condenser connected across saidresistor, and a set oi vibratory contacts connected across both saidresistor and said device.

11. In combination, a direct current excitation circuit for adynamo-electric machine, a regulating resistor connected in saidcircuit, a unidirectional conducting device connected in said circuitelectrically adjacent said resistor with its direction of conductivitythe same as the direction 0! normal current fiow in said circuit, acondenser connected across said resistor, and a regulator having a pairof contacts connected across both said resistor and said unidirectionalconducting device in series.

12. In combination, a direct current excitation tion of normal currentflow in said field winding, circuit for a shunt connected field windingof a a condenser connected across said resistor. and a direct currentgenerator, a resistor in series with vibratory contact voltage regulatorhaving a pair said field windingi a unidirectional conducting ofcontacts connected across t said e tor device connected in series withsaid field winding d d di ct a nd c dev ce in 5 and electricallyadjacent said resistor with its Se es. direction of conductivity thesame as the direc- BERNARD M. CAIN.

